International study shows drylands need ‘plant species richness’

A massive collaborative research project, involving 53 scientists on six continents, has proved the importance of maintaining a rich variety of plant species in ecosystems in dry and arid regions.

In the first global study of its kind, the scientists studied 224 dryland sites in 15 countries. They found that a study site’s “plant species richness” was directly related to its “multifunctionality” – its ability to perform a number of simultaneous functions related to the cycling and storage of carbon, nitrogen and phosphorus.

In their paper published today in the international journal Science, the researchers say their results “suggest that preservation of plant biodiversity is crucial to buffer negative effects of climate change and desertification in drylands”.

Dr Matthew Tighe, a lecturer in the School of Environmental and Rural Science at the University of New England, contributed to the project with sites in – and data from – central and western NSW. “The Australian component of the project was important,” Dr Tighe said, “because Australia is one of relatively few countries having large arid and semi-arid areas where agriculture is not at the subsistence level.” The other countries included in the study were Argentina, Brazil, Chile, China, Ecuador, Iran, Israel, Mexico, Morocco, Peru, Spain, Tunisia, the United States and Venezuela. (For details of the paper’s authors and their affiliations go to: http://www.sciencemag.org/content/335/6065/214.abstract.)

“The work involved selecting representative sites, identifying the range of plant species present, and collecting soil samples to monitor a total of 14 ‘functions’, including soil biological activity and soil carbon levels and cycling,” Dr Tighe explained. “All of the measures are important aspects of the system, but their combined importance is reflected in plant species richness.”

Statistical analysis of the major variable factors (including climate and the physical environment) that affect ecosystem multifunctionality found that plant species richness was one of the most dominant factors overall.

The paper (Maestre et al: “Plant species richness and ecosystem multifunctionality in global drylands”, Science Vol. 335 pp. 214-218) notes that drylands cover 41 per cent of Earth’s land surface, support 38 per cent of the global human population, and are home to many endemic plant and animal species. These ecosystems are “highly vulnerable to global environmental change and desertification”, the authors say.

They conclude that, in the event of the dryland temperature increases predicted by climate change models, maintaining plant species richness “may be particularly important for maintaining ecosystem functions linked to carbon and nitrogen cycling that sustain carbon sequestration and soil fertility”.